The promise of a vaccine to protect against malaria gives a lot of hope. But it feels a lot better to know that a study has begun in Kenya on how a vaccine can prevent malaria in human immunodeficiency virus (HIV) positive children, with preliminary results expected soon.The study, Mal 58, has enrolled a total of 200 children and is conducted by the United States Army Medical Research Unit (USAMRU), Walter Reed Project in Kombewa in Kisumu County and at the Siaya Kenya Medical Research Institute KEMRI)/ CDC Clinical Trial Centre in Siaya County.
Children are vulnerable to malaria, and those who are HIV- positive are at greater risk of dying from the disease due to their compromised immune systems.
Principal Investigator at the Walter Reed Project, Dr. Walter Otieno, spoke about progress on the malaria vaccine at a symposium organised by Internews Kenya.
Dr. Otieno said the RTS,S malaria vaccine, expected to be in use in the near future, is studied to know how safe and efficacious it is for children living with HIV.
“The malaria vaccine is expected to be rolled out in the entire country and to children regardless of their HIV status and this is why we have decided to carry out this research to see whether this vaccine is safe and efficacious to children who are living with the HIV,” Dr. Otieno said.
“This vaccine represents a first generation vaccine that offers around half protection, while more research is being carried out to find a second generation vaccine by 2025 that would offer around 80 per cent protection and last longer than four years,” Dr. Otieno added.
The great role played by vaccines in the elimination of killer diseases like smallpox has actuated scientists to find a vaccine for malaria to help eradicate the disease.
Fortunately, progress has been made in this direction and within a couple of years the first ever malaria vaccine is likely to be deployed to save lives in the expanded programme on immunisation (EPI).
World renowned medical professor Hans Rosling recently remarked that "We used to have a developing world with high child mortality against an industrialised world with low mortality, but that is changing and one of the drivers is the gradual access to vaccines.”
The Swedish medical doctor, academic and statistician Rosling was only echoing the general feeling among stakeholders that vaccines are the most cost-effective tools for addressing public health issues and have historically contributed to a reduction in the spread and burden of infectious diseases.
As the world prepares for a possible introduction of a malaria vaccine into the EPI in 2015, considerations are being made to ensure that every child at risk of malaria receives the necessary protection.
Meanwhile, the World Health Organisation (WHO) has issued a statement on the efficacy and safety of the RTS,S, commenting on the possible hypotheses for differences in the efficacy of the vaccine in the 2 age groups of infants and children.
"Lower immune responses are induced by the vaccine in infants aged 6-14 weeks (basic vaccination age for infants) compared to children aged 5-17 months. The reasons for this difference are unclear but co-administration with other vaccines and the presence of maternally-acquired antibodies to malaria in the 6-14 week olds may both be factors related to this difference," the WHO statement said.
"Any possible recommendation related to vaccination later than the first few months of life would require at least 2 additional immunization visits to be added to the routine immunization schedule.”
Some scientists contend that some vaccines are not effective for long in very young children because their immune systems are very active and clear the vaccine.
The duration of immunity provided by vaccines varies depending on a range of factors, particularly the vaccine itself.
There is also talk that immune persistence can be limited in the very young and very old and as immunity wanes people become firstly susceptible to symptoms from mild clinical disease then to more severe disease.
The duration of immunity offered by the malaria vaccine is still being discussed. Some experts point to how the vaccine for measles gives lifelong protection. Mumps vaccine also has a long-term duration.
The RTS,S vaccine's protection is said to last for a year or less, but there is comfort in the fact that like most vaccines, the aim is to get beneficiaries through childhood when these diseases are most deadly.
The impact of child vaccines is magnified when used in conjunction with other health efforts like antibiotics, oral rehydration salts, bed nets, and vitamins.
The malaria map is rapidly shrinking. In 1900, endemic malaria was present in almost every country. The disease has been eliminated in 111 countries and 34 countries are advancing towards elimination, according to a publication in the Lancet global health journal.
Vaccines can cause “herd immunity”, which means if the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get sick because others are less likely to get sick and spread the disease.
Researchers estimate that a viable malaria vaccine could be ready for children in the developing world as early as 2015.
RTS,S will be submitted to the European Medicines Agency (EMA) under article 58 because it is being developed by an EU manufacturer specifically for targeted populations and against a disease which occurs primarily outside the EU. It is not expected that the
manufacturer will seek
to license this vaccine in European countries given its targeted intended use.
The WHO describes a vaccine as a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing micro-organism in a weakened or killed form, its toxins or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these micro-organisms it encounters in the future.
The global health body also explains that current vaccines against human diseases are caused by either viruses or bacteria. Should RTS,S be licensed, it will be the first-ever licensed vaccine against a parasitic disease in humans.
By Dickson Odhiambo-Kisumu, Kenya